Recycling method

ABSTRACT

A method of the present invention for producing a halohydantoin compound by refining, in a dryer ( 1 ), a composition containing at least one of water and elemental halogen, an organic solvent, and the halohydantoin compound, the method includes the steps of: (i) removing the organic solvent from the composition; and (ii) removing the at least one of the water and the elemental halogen from the composition refined in the step (i).

TECHNICAL FIELD

The present invention relates to a method and an apparatus each forproducing a halohydantoin compound, a recycling system and ahalohydantoin compound.

BACKGROUND ART

Halohydantoin compounds have been widely used as a sensitizer for aphotograph or the like or as a halogenating agent or an oxidizing agentfor use in a process of producing a medicinal product, an agriculturalchemical, a chemical compound, or the like. The halohydantoin compoundsare considered as a promising compound because the halohydantoincompounds are stable and can be more economically produced by a knownmethod. One of such halohydantoin compounds is1,3-diiodo-5,5-dimethylhydantoin. As a method for producing1,3-diiodo-5,5-dimethylhydantoin, for example, a method including thestep of causing 5,5-dimethylhydantoin and iodine monochloride to reactwith each other in the presence of a base in a mixed solvent of anaqueous solution of a base and an organic solvent and a refining methodhave been disclosed (see, for example, Patent Literature 1 andNon-Patent Literature 1).

Non-Patent Literature 1 describes the following method:5,5-dimethylhydantoin and iodine monochloride are reacted with eachother with use of a sodium hydroxide aqueous solution and carbontetrachloride. The resulting crystals are washed with water, and arefurther washed with anhydrous ethyl acetate. After that, the crystalsare dried at 60° C. under a reduced pressure and thereby,1,3-diiodo-5,5-dimethylhydantoin is refined. Non-Patent Literature 1further states that the resulting 1,3-diiodo-5,5-dimethylhydantoin is areagent so stable that it can be preserved without recrystallizing in adesiccator in a dark place.

Further, Patent Literature 1 gives the following description: First,5,5-dimethylhydantoin and iodine monochloride are reacted with eachother in a sodium hydroxide aqueous solution with use ofN,N-dimethylformamide or an n-butyl acetate solvent. Next, theprecipitated crystals as a result of the reaction are collected byfiltration, and then, dried under a reduced pressure, thereby beingrefined.

CITATION LIST

Patent Literature 1

-   Japanese Patent Application Publication, Tokukai, No. 2002-30072 A    (Publication Date: Jan. 29, 2002)

Non-Patent Literature 1

-   ORFEO O. ORAZI., et al., N-Iodohydantoins. II. Iodinations with    1,3-Diiodo-5,5-dimethylhydantoin, J. Org. Chem., 1965, Vol. 30, p.    1101-1104

SUMMARY OF INVENTION Technical Problem

With the refining method described in Non-Patent Literature 1,1,3-diiodo-5,5-dimethylhydantoin contains 65% of effective iodine, andthe yield of 1,3-diiodo-5,5-dimethylhydantoin is as low as 75%.Non-Patent Literature 1 makes no mention of the purity of1,3-diiodo-5,5-dimethylhydantoin.

Further, Patent Literature 1 makes no mention of the purity of1,3-diiodo-5,5-dimethylhydantoin that is obtained by the refining methoddescribed therein.

The inventors of the present invention diligently studied the methodsfor refining a halohydantoin compound described in these literatures. Asa result, the inventors of the present invention finally found thefollowing problems:

A halohydantoin compound is so unstable at a normal temperature that thehalohydantoin compound needs to be refrigerated for preservation.Further, when suspended in water, a halohydantoin compound graduallydecomposes to liberate iodine. Furthermore, when heated in the statebeing a wet material containing a certain or lager amount of a mixedliquid component such as a mixture of water and an organic solvent, ahalohydantoin compound problematically becomes more unstable. Thehalohydantoin compound consequently decomposes to liberate a hydantoincompound and iodine. This undesirably causes a decrease in purity of thehalohydantoin compound. Further, the iodine thus liberated undesirablycauses coloring of the halohydantoin compound and corrosion of refiningequipment.

The present invention has been made in view of the foregoing problems,and it is an object of the present invention to provide a method forproducing a halohydantoin compound by removing a component such as anorganic solvent from a composition containing the halohydantoin compoundwhile inhibiting the halohydantoin compound from decomposing to invitecoloring of the halohydantoin compound and corrosion of the equipment.

Solution to Problem

In order to solve the above problem, the inventors of the presentinvention made diligent studies and as a result found out that when ahalohydantoin compound containing an organic solvent is dried at a hightemperature, decomposition of the halohydatoin compound is accelerated.Consequently, the inventors of the present invention have attained thepresent invention.

In other words, a production method of the present invention is attainedin view of the above object and the production method is a method forproducing a halohydantoin compound by refining, in a dryer, acomposition containing at least one of water and elemental halogen, anorganic solvent, and the halohydantoin compound, the method includingthe steps of: (i) removing the organic solvent from the composition, ata temperature in a range of not less than 15° C. and not greater than60° C.; and (ii) removing the at least one of the water and theelemental halogen from the composition refined in the step (i).

A production apparatus of the present invention is attained in view ofthe above object, and the apparatus is an apparatus for producing ahalohydantoin compound, the apparatus refining a composition containingat least one of water and elemental halogen, an organic solvent, and thehalohydantoin compound, the apparatus including: a dryer for drying thecomposition so as to remove a component except the halohydantoincompound from the composition; pressure control means for controlling apressure in the dryer; a collection tank for collecting the componentremoved from the composition, the collection tank being connected to thedryer via a duct; and heating means for heating the duct.

A recycling system of the present invention is attained in view of theabove object and the recycling system is a system having the steps ofrefining a composition containing at least one of water and elementalhalogen, an organic solvent, and a halohydantoin compound and recoveringa component removed by refining, the recycling system including thesteps of: (a) preparing the composition; (b) after the step (a),removing first the organic solvent from the composition and then atleast one of the water and the elemental halogen from the composition;and (c) collecting the component removed in the step (b) and recoveringthe component collected, for use in the step (a) to be newly carriedout.

A halohydantoin compound of the present invention is arranged so as tohave a water content of not greater than 3 weight %.

Advantageous Effects of Invention

The present invention advantageously makes it possible to produce ahalohydantoin compound by removing a component such as an organicsolvent from a composition containing the halohydantoin compound whileinhibiting the halohydantoin compound from decomposing to invitecoloring of the halohydantoin compound and corrosion of equipment.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view schematically illustrating an arrangement of oneembodiment of a production apparatus according to the present invention.

DESCRIPTION OF EMBODIMENTS

A production method of the present invention is for producing ahalohydantoin compound by refining, in a dryer, a composition containingat least one of water and elemental halogen, an organic solvent, and thehalohydantoin compound, and includes the first step (i) of removing theorganic solvent from the composition, at a temperature in a range of notless than 15° C. and not greater than 60° C. and the second step (ii) ofremoving the at least one of the water and the elemental halogen fromthe composition refined in the first step.

As described above, the halohydantoin compound is unstable when thehalohydantoin compound is in the form of a wet material containing aliquid component to a certain extent. On this account, a method fordrying this wet material has been provided. However, when the wetmaterial is dried by heating under a reduced pressure so that the wetmaterial is refined, the halohydantoin compound becomes more unstable.As a result, the halohydantoin compound is decomposed. Consequently, thehydantoin compound and elemental halogen are liberated. This decreases apurity of the halohydantoin compound. Moreover, the halohydantoincompound is colored by thus liberated elemental halogen.

In order to solve the above problem, the inventors of the presentinvention have made diligent studies. As a result, the inventors of thepresent invention found out that when a halohydantoin compoundcontaining an organic solvent and elemental halogen is dried at a hightemperature under a reduced pressure, decomposition of the halohydantoincompound is accelerated. The inventors of the present invention haveconsequently attained the present invention.

(Composition)

In the production method of the present invention, a composition that isa subject of treatment contains (i) at least one of water and elementalhalogen, (ii) an organic solvent, and (iii) a halohydantoin compound.The other components except the halohydantoin compound in thecomposition, that is, the water, the elemental halogen, and the organicsolvent each are a substance whose vapor pressure at 25° C. is not lessthan 35 Pa. In regard to a content of these substances relative to theentire composition, for example, a lower limit value is preferably 2weight %, more preferably 5 weight %, or even more preferably 8 weight%, while an upper limit value is preferably weight %, more preferably 45weight %, or even more preferably 40 weight %. It is possible tosuitably use, in particular, a composition whose content of a liquidcomponent including water and the organic solvent is not less than 2weight % and not greater than 50 weight %. By treating, according to theproduction method of the present invention, such a compositioncontaining the other components in the above range, it is possible toproduce a halohydantoin compound by removing a component such as anorganic solvent from a composition containing the halohydantoincompound, while inhibiting the halohydantoin compound from decomposingto invite coloring of the halohydantoin compound and corrosion ofequipment.

Note that the term “composition” in the present specification indicatesa composition containing a liquid component in the above range and mayalso be called a “wet material”. Further, a compound containing lessthan 5 weight % of the liquid component as a result of treatmentaccording to the production method of the present invention may besimply referred to as a halohydantoin compound.

In the present specification, the halohydantoin compound can berepresented by the following chemical formula I. Note that in thefollowing chemical formula I, a combination of R₁, R₂, X₁ and X₂ may beany combination as long as the above range is satisfied.

where:

R₁ and R₂ are either identical to or different from each other, and are(i) each independently H, a substituted or unsubstituted C1 to C10aliphatic hydrocarbon group, a substituted or unsubstituted C3 to C10alicyclic hydrocarbon group, or a substituted or unsubstituted C6 to C10allyl group or aralkyl group, more preferably H or a C1 to C8 aliphatichydrocarbon group, or even more preferably H or a methyl group, or (ii)most preferably both methyl groups; and

X₁ and X₂ are either identical to or different from each other, and are(i) each independently H or a halogen atom, more preferably H, Br, or I,or even more preferably H or I, or (ii) most preferably both I,

excluding a halohydantoin compound wherein X₁ and X₂ are both H.

More specifically, preferable examples of the halohydantoin compoundencompass 1-bromohydantoin, 1-iodohydantoin, 3-bromohydantoin,3-iodohydantoin, 1,3-dibromohydantoin, 1,3-diiodo hydantoin,1-bromo-5-methylhydantoin, 1-iodo-5-methylhydantoin,3-bromo-5-methylhydantoin, 3-iodo-5-methylhydantoin,1,3-dibromo-5-methylhydantoin, 1,3-diiodo-5-methylhydantoin,1-bromo-5,5-dimethylhydantoin, 1-iodo-5,5-dimethylhydantoin,3-bromo-5,5-dimethylhydantoin, 3-iodo-5,5-dimethylhydantoin,1,3-dibromo-5,5-dimethylhydantoin, and 1,3-diiodo-5,5-dimethylhydantoin.

Note that all halohydantoin compounds contained in the composition maybe identical in composition or alternatively, the above-describedplurality of types of composition of the halohydantoin compound may bemixedly present in the composition.

A method for obtaining the halohydantoin compound is not particularlylimited, but the halohydantoin compound may be synthesized according toa conventionally known method. One example of a method for synthesizingthe halohydantoin compound includes the step of reacting a hydantoincompound and elemental halogen in the presence of a base in an aqueoussolution. For example, by reacting a hydantoin compound and an alkalimetal salt (NaOH or KOH) with each other, a hydantoin metal salt isprepared. Then, this hydantoin metal salt is reacted with iodinemonochloride (ICl) or iodine monobromide (IBr). This gives a wetmaterial including a halohydantoin compound, that is, a composition tobe treated in the present invention.

As the elemental halogen, for example, at least one kind from amongiodine, bromine and chlorine can be employed. As the organic solvent,for example, at least one kind of the following organic solvents can beemployed: an ester solvent, an aromatic solvent, an ether solvent and achlorine solvent each having a boiling point in a range of not less than30° C. and not greater than 200° C.

Note that examples of the ester solvent encompass methyl acetate, ethylacetate, propyl acetate, isopropyl acetate, butyl acetate, isobutylacetate, sec-butyl acetate, tert-butyl acetate, pentyl acetate, hexylacetate, methyl propionate, ethyl propionate, propyl propionate, butylpropionate, methyl butyrate, ethyl butyrate, propyl butyrate, and butylbutyrate.

Examples of the aromatic solvent encompass benzene, toluene, ethylbenzene, propyl benzene, cumene, butyl benzene, isobutyl benzene,sec-butyl benzene, tert-butyl benzene, o-xylene, m-xylene, p-xylene,mesitylene, 1,2,3-trimethyl benzene, 1,2,4-trimethyl benzene, o-cymene,m-cymene, and p-cymene.

Examples of the ether solvent encompass diethyl ether, dipropyl ether,isopropyl ether, methyl-tert-butyl ether, methyl cyclopentyl ether,dibutyl ether, anisole, ethyl phenyl ether, tetrahydrofuran,tetrahydropyran, and 1,4-dioxane.

Examples of the chlorine solvent encompass chloropropane, chlorobutane,chloropentane, chlorohexane, chloroheptane, chlorooctane,dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane,1,3-dichloropropane, 2,2-dichloropropane, 1,2-dichlorobutane,1,3-dichlorobutane, 1,4-dichlorobutane, chloroform,1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,1,2-tetrachloroethane,1,1,2,2-tetrachloroethane, 1,2,3-trichloropropane, and carbontetrachloride.

The following discusses one embodiment of the production method of thepresent invention, by using a production apparatus 10 shown in FIG. 1.FIG. 1 is a view schematically illustrating one embodiment of aproduction apparatus of the present invention.

(Arrangement of Production Apparatus 10)

First, the following discusses an arrangement of the productionapparatus 10. The production apparatus 10 is arranged to include a dryer1, a collection tank 2 and a pressure reducing pump (pressure controlmeans) 3.

The dryer 1 is for drying a composition (hereinafter, referred to as a“wet material”) containing at least one of water and elemental halogen,an organic solvent, and a halohydantoin compound. For example, thepurity of the halohydantoin compound can be increased by first reducingthe pressure in the dryer 1, and then drying the wet material by heatingwhile rotating the dryer 1 and thereby removing a component except thehalohydantoin compound. The dryer 1 includes a container in which thewet material is contained, and is arranged so that the interior of thecontainer can be heated with hot water running around the container.Further, a pressure in the dryer 1 is controlled by the pressurereducing pump 3 described below. Note that a method for controlling atemperature and the pressure in the dryer 1 is not limited to the abovemethod.

Various dryers can be used as the dryer 1. For example, as the dryer 1,a rotary container vacuum dryer (conical vacuum dryer, conical dryer), arotary drum vacuum dryer (drum vacuum dryer), a vacuum belt dryer, atray vacuum dryer or a tray reduced-pressure dryer, etc. are suitablyused. In particular, the rotary container vacuum dryer (conical vacuumdryer) or the rotary drum vacuum dryer (drum vacuum dryer) arepreferable for the following reasons: (i) the rotary container vacuumdryer (conical vacuum dryer) or the rotary drum vacuum dryer (drumvacuum dryer) can stir contents of the dryer 1, so that dryingefficiency can be improved and agglomeration and lack of uniformity indrying can be prevented; and (ii) the rotary container vacuum dryer(conical vacuum dryer) or the rotary drum vacuum dryer (drum vacuumdryer) is a compact device.

The dryer 1 is connected with the collection tank 2 via a duct 4 a sothat a gaseous component removed in the dryer 1 can be sent into thecollection tank 2. Moreover, between the dryer 1 and an end of the duct4 a which end is connected to the dryer 1 (that is, a section connectingthe dryer 1 and the duct 4 a), a filter (filtering means, usually madeof fluororesin) 6 is provided so that gas (vaporized component) to besent to the collection tank 2 is filtered. The presence of this filter 6prevents (i) a solid substance scattered in the dryer 1 from causingblockage in a reduced pressure lines (ducts 4 a and 4 b) during dryingand (ii) pollution or corrosion of the collection tank 2 or the pressurereducing pump 3, thereby consequently improving a collection rate of atarget object.

Note that the dryer 1 may be additionally provided with, for example, aninlet for introducing an inert gas into the dryer 1. This makes itpossible to reduce the pressure in the dryer 1 to a pressure lower thanthe atmospheric pressure while introducing the inert gas into the dryer1. The inert gas may be any gas as long as the inert gas is inert withrespect to the halohydantoin compound. Examples of the inert gasencompass the air, nitrogen, helium, argon, carbon dioxide, etc.

The duct 4 a is housed in a tubular pipe (heating means, not shown) andheated by flow of the warm air through the pipe. This makes it possibleto prevent a lump of iodine from blocking in the duct 4 a. Note thatmeans for heating the duct 4 a is not limited to the above arrangement.Further, for the duct 4 a, the production apparatus 10 is provided withmanometers 5 a and 5 b for monitoring difference between the pressure inthe dryer 1 and the pressure in the duct 4 a, and a sight glass 7 forchecking blockage in the duct 4 a.

The collection tank 2 is a tank for collecting the component removedfrom the wet material. The collection tank 2 is connected with the duct4 a so that gas discharged from the dryer 1 is sent into the collectiontank 2. One collection tank or a plurality of collection tanks may beprovided as the collection tank(s) 2. In the present embodiment, twocollection tanks (2 a and 2 b) are provided in series with each other.Specifically, the collection tank 2 a is arranged so that the interiorof the collection tank 2 a is empty and iodine contained in the gas sentin is collected in the collection tank 2 a. Meanwhile, liquid forabsorbing gas is contained in the collection tank 2 b so that elementalhalogen (i.e., bromine or chlorine) except iodine, water, an organicsolvent, and iodine that has not been collected in the collection tank 2a are collected in the collection tank 2 b. As the liquid contained inthe collection tank 2 b, for example, a reducing-agent containingaqueous solution or an organic solvent can be employed.

Note that although the interior of the collection tank 2 a is empty andliquid is contained in the collection tank 2 b in the presentembodiment, liquid may be contained in the collection tank 2 a. In thiscase, the production apparatus 10 may be arranged to have only onecollection tank, and elemental halogen except iodine, water, and anorganic solvent are collected in the collection tank 2 a. Further, thecollection tank 2 b may contain liquid, and the liquid may be circulatedthrough the collection tank 2 b by once taking the liquid out from thecollection tank 2 b and pouring the liquid like a shower back into thecollection tank 2 b. Alternatively, the collection tank 2 a may containliquid, and the liquid may be circulated through the collection tank 2 aby once taking the liquid out from the collection tank 2 a and pouringthe liquid like a shower back into the collection tank 2 a. As a furtheralternative, both the collection tanks 2 a and 2 b may contain liquid,and the liquid may be circulated through the collection tanks 2 a and 2b by once taking the liquid out from the collection tanks 2 a and 2 band pouring the liquid like a shower back into the collection tanks 2 aand 2 b.

The pressure reducing pump 3 is a pump for controlling the pressure inthe dryer 1. The pressure reducing pump 3 is connected to the collectiontank 2 via the duct 4 b, so that the pressure reducing pump 3 reducesthe pressure in the dryer 1 via the collection tank 2 and the ducts 4 aand 4 b. Note that the reduced pressure in the dryer 1 is returned to anordinary pressure, for example, with nitrogen.

Note that the production apparatus of the present embodiment may bearranged to include, for example, a control system. In this case,various types of processing in the production apparatus can be automatedby use of the control system.

Next, the following discusses one embodiment of the production method ofthe present invention, by using, as an example, a case where theproduction method of the present invention is carried out in theproduction apparatus 10.

(First Step)

The first step of the production method of the present invention is thestep of removing the organic solvent from the wet material in the dryer1. In this first step, the wet material is put in the dryer 1. Then, thepressure in the dryer 1 is reduced to a pressure lower than theatmospheric pressure by the pressure reducing pump 3. Then, while thedryer 1 is being rotated, the temperature in the dryer 1 is increased byheating and thereby, the organic solvent is vaporized and removed fromthe wet material. Note that in the present example, the wet material isdried by employing a conical vacuum dryer while the conical vacuum dryeris being rotated. However, the method for drying the wet material is notlimited to this arrangement.

In the first step, at least one of the temperature and the pressure inthe dryer 1 may be set lower than that in the second step describedbelow. For example, the lower limit value of the temperature in thedryer 1 in the first step is preferably 15° C., more preferably 25° C.,or even more preferably 35° C., while the upper limit value of thetemperature in the dryer 1 in the first step is preferably 60° C., morepreferably 55° C., or even more preferably 50° C. Meanwhile, forexample, the lower limit value of the pressure in the dryer 1 in thefirst step is preferably 0.1 kPa, more preferably 0.3 kPa, or even morepreferably 0.5 kPa, while the upper limit value of the pressure in thedryer 1 in the first step is preferably 20 kPa, more preferably 15 kPa,or even more preferably 10 kPa.

The organic solvent removed from the dryer 1 is sent into the collectiontank 2 a and 2 b via the duct 4 a. As described above, in the presentexample, the interior of the collection tank 2 a is empty while thecollection tank 2 b contains liquid. Therefore, the organic solvent sentthrough the duct 4 a is collected in the collection tank 2 b.

In this way, in the first step, at least one of the temperature and thepressure is set lower than that in the second step. This makes itpossible to remove, from the wet material, mainly the organic solventand elemental halogen. As described above, when the halohydantoincompound containing the organic solvent and elemental halogen is driedat a high temperature under a reduced pressure, decomposition of thehalohydantoin compound is accelerated. This decreases the purity of thehalohydantoin compound and/or causes coloring of the halohydantoincompound or corrosion of equipment due to the liberated elementalhalogen (mainly, iodine). According to the present invention, first, theorganic solvent and elemental halogen are removed at a lower temperatureunder a lower pressure. This makes it possible to prevent decompositionof the halohydantoin compound from accelerating.

Note that, for example, whether or not a content of the organic solventor elemental halogen contained in the wet material becomes not more thana predetermined value can be used as a criterion for determining when toend the first step. Such a criterion can be set as appropriate accordingto properties and states of what to be prepared. For example, whether ornot the content of the organic solvent in the composition (hereinafter,“crude dried product”) refined in the first step becomes preferably notgreater than 0.5 weight %, or more preferably not greater than 0.2weight % can be used as a criterion for determining when to end thefirst step. In a case where the content of the organic solvent in thecomposition refined in the first step is not greater than 0.5 weight %,decomposition of the halohydantoin compound can also be prevented at thetemperature set in the second step. Alternatively, for example, whetheror not the content of elemental halogen in the crude dried productbecomes preferably not greater than 0.75 weight % or more preferably,not greater than 0.5 weight % can be used as a criterion for determiningwhen to end the first step. When the content of elemental halogen in thecomposition refined in the first step is not greater than 0.75 weight %,decomposition of the halohydantoin compound can also be prevented at thetemperature set in the second step. Further, after the first step hasended, the reduced pressure in the dryer 1 may be returned to anordinary pressure and then the pressure is reduced again when the stepshifts to the second step.

(Second Step)

The second step in the production method of the present invention is thestep of removing at least one of water and elemental halogen from thecrude dried product having been refined in the dryer 1. In the secondstep, the pressure in the dryer 1 containing the crude dried product isreduced by use of the pressure reducing pump 3 and the temperature inthe dryer 1 is increased by heating while the dryer 1 is being rotated.At this time, at least one of the temperature and the pressure in thedryer 1 is set higher than that in the first step. This makes itpossible to remove at least one of water and elemental halogen from thecrude dried product.

For example, the lower limit value of the temperature in the dryer 1 inthe second step is preferably 60° C., more preferably 70° C., or evenmore preferably 75° C., while the upper limit value of the temperaturein the dryer 1 in the second step is preferably 100° C., more preferably95° C., or even more preferably 90° C. Meanwhile, for example, the lowerlimit value of the pressure in the dryer 1 in the second step ispreferably 0.1 kPa, more preferably 0.3 kPa, or even more preferably 0.5kPa, while the upper limit of the pressure in the dryer 1 in the secondstep is preferably 25 kPa, more preferably 20 kPa, or even morepreferably 15 kPa.

The water and elemental halogen removed from the dryer 1 is sent intothe collection tanks 2 a and 2 b via the duct 4 a. In the presentexample, in the empty collection tank 2 a, iodine among elementalhalogens is collected. Meanwhile, in the collection tank 2 b containingliquid, elemental halogens except iodine and water are collected.

As described above, in the second step, at least one of the temperatureand the pressure is set higher than that in the first step. This makesit possible to remove mainly water and elemental halogen from the crudedried product. Because the crude dried product is dried by heating at asufficiently high temperature under a sufficiently high pressure, thehalohydantoin compound can be made into a more stable dried product.Further, when the second step is carried out, the organic solvent hasalready been removed from the crude dried product. Accordingly, evenwhen the drying by heating is carried out at a high temperature,acceleration of decomposition of the halohydantoin compound issuppressed. This makes it possible to produce a highly-purehalohydantoin compound that is less colored.

Even in a case where the method of the present invention is employed,part of the halohydantoin compound may be decomposed during drying andconsequently, elemental halogen may be produced. However, according tothe present invention, thus produced elemental halogen can also besuitably removed during drying. Accordingly, even in the case of acomposition containing elemental halogen initially (i.e. in the wetmaterial), the elemental halogen can be suitably removed by the methodof the present invention and a highly-pure halohydantoin compound can beobtained by refinement.

Note that, for example, whether or not a content of water contained inthe crude dried product becomes not more than a predetermined value canbe used as a criterion for determining when to end the second step. Sucha criterion can be set as appropriate according to properties and statesof what to be prepared. For example, whether or not the content of waterin the dried product in the second step becomes preferably not greaterthan 3.0 weight %, more preferably not greater than 2.0 weight %, ormost preferably 1.0 weight % can be used as a criterion for determiningwhen to end the second step.

According to the method of the present invention for producing ahalohydantoin compound, it is possible to obtain a halohydantoincompound (i) which is suitably dried so that an organic solvent andelemental halogen are removed, and (ii) which has the water content ofnot greater than 3 weight %. When the water content is not greater than3 weight %, the halohydatoin compound can be stored withoutdeterioration in purity for not less than one year by refrigerationstorage at the temperature of 5° C.

The method of the present invention for producing a halohydantoincompound may further include an additional step following the end of thesecond step. The additional step may be, for example, the step offurther removing at least one of water and elemental halogen, or anorganic solvent from the composition.

(Recycling System)

The present invention also provides a system for recycling the organicsolvent and the elemental halogen that are removed from the compositionand collected in the above-described production method.

A recycling system of the present invention is a system having the stepsof refining a composition containing at least one of water and elementalhalogen, an organic solvent, and a halohydantoin compound and recoveringa component removed by refining, the recycling system including thesteps of: (a) preparing the composition; (b) after the step (a),removing first the organic solvent from the composition and then atleast one of the water and the elemental halogen from the composition;and (c) collecting the component removed in the step (b) and recoveringthe component collected, for use in the step (a) to be newly carriedout.

The step (a) is for preparing a composition containing at least one ofwater and elemental halogen, an organic solvent, and a halohydantoincompound. The composition prepared here may be the wet material in thedescription of the production method of the present invention. As amethod for preparing the composition, it is possible to employ thesynthesis method described above.

The step (b) is for removing, after the step (a), first the organicsolvent from the composition and then at least one of the water and theelemental halogen. More specifically, it is possible to apply, to thisstep (b), procedures for the first step and the second step in theproduction method of the present invention.

The step (c) is for collecting the component removed in the step (b) andrecovering the component collected, for use in the step (a) to be newlycarried out. As the method for collecting the component removed, it ispossible to employ the method discussed in the production method of thepresent invention. Further, how the component is recovered is notparticularly limited. For example, it is possible to provide in advanceducts respectively for taking out the organic solvent and the elementalhalogen so that the ducts are connected to the collection tanks 2 a and2 b of the production apparatus 10 as illustrated in FIG. 1, and takeout the organic solvent and the elemental halogen through the ducts.This makes it possible to recycle thus recovered component in the stepof preparing a composition to be newly carried out.

Note that the step (a) of preparing a composition to be newly carriedout here indicates the step (a) of newly preparing a composition afterthe step (c) of recovering the component, that is, the step ofsynthesizing a wet material containing a halohydantoin compound. In thisstep (a) of preparing a composition to be newly carried out, thecomposition can be synthesized by use of the component recovered in thestep (c) of recovering the component.

The following discusses in more detail the embodiment of the presentinvention, providing Examples. Needless to say, the present invention isnot limited to the Examples below, and may take various embodiments interms of details. Further, the present invention is not limited to thedescription of the embodiment above, but may be altered in various waysby a skilled person within the scope of the claims. Any embodiment basedon a proper combination of technical means disclosed is also encompassedin the technical scope of the present invention.

As described above, according to the production method of the presentinvention, in the first step (i) of removing the organic solvent fromthe composition, more preferably, the content of the organic solvent isdecreased to a range of not greater than 0.5 weight %.

Further, in the production method of the present invention, in the firststep (i) of removing the organic solvent from the composition, morepreferably, the elemental halogen is removed so that a content of theelemental halogen is decreased to a range of not greater than 0.75weight %.

Further, in the production method of the present invention, morepreferably, at least one of the temperature and the pressure in thedryer is set lower in the first step (i) than in the second step (ii).

Further, in the production method of the present invention, morepreferably, the temperature in the first step (i) is in a range of notless than 15° C. and not greater than 60° C., and the temperature in thesecond step (ii) is in a range of not less than 60° C. and not greaterthan 100° C.

Further, in the production method of the present invention, morepreferably, in the first step (i), the pressure is in a range of notless than 0.1 kPa and not greater than 20 kPa; and in the second step(ii), the pressure is in a range of not less than 0.1 kPa and notgreater than 25 kPa.

Further, in the production method of the present invention, the organicsolvent can suitably be at least one selected from among an estersolvent, an aromatic solvent, an ether solvent, and a chlorine solventeach having a boiling point in a range of not less than 30° C. and notgreater than 200° C. under an atmospheric pressure.

Further, in the production method of the present invention, theelemental halogen can suitably be at least one selected from amongiodine, bromine and chlorine.

Further, according to the production method of the present invention,more preferably, the halohydantoin compound is a compound represented bythe chemical formula I above.

Further, more preferably, the production apparatus of the presentinvention further includes filtering means for filtering the componentvaporized, the filtering means being connected to a connecting sectionbetween the dryer and the duct.

Further, in the production apparatus of the present invention, morepreferably, the collection tank contains liquid for absorbing thecomponent vaporized.

Further, in the production apparatus of the present invention, morepreferably, the liquid is either a reducing-agent containing aqueoussolution or an organic solvent.

EXAMPLES

Quantitative determination of 1,3-diiodo-5,5-dimethylhydantoin wasperformed by a titration method with a 0.1 N aqueous solution of silvernitrate, and quantitative determination of butyl acetate was performedby an internal reference method of gas chromatography. Quantitativedetermination of elemental iodine extracted from a sample with use ofchloroform was performed by a silver nitrate titration method. The watercontent was a value obtained by subtracting the content of elementaliodine from the content of a volatile substance. This content of thevolatile substance was obtained by measuring a decrease in mass of asample in a case where the sample was subjected to 2-hour drying at 105°C. under the atmospheric pressure according to “First Method: Method forDrying by Heating under Atmospheric Pressure” in JIS-K0067-19924.1.4(1). This is because, although it is usual to measure a watercontent by using the Karl Fisher apparatus, the present sample isreactive to a Karl Fisher solution and therefore the water content ofthe present sample cannot be measured

Production Example 1: Synthesis of 1,3-diiodo-5,5-dimethylhydantoin

First, a composition containing 1,3-diiodo-5,5-dimethylhydantoin(halohydantoin compound) was produced by the following procedures.

First, water (350.5 kg) was fed into a 1000-L glass lining reaction potand secondly 12.0% by weight of NaOH aqueous solution (81.7 kg) was fedinto the same reaction pot. Then, 5,5-dimethylhydantoin (31.4 kg, 245.0mol) was fed into the reaction pot. After that, the mixture was cooledto 6° C.

Next, while a temperature of contents of the reaction pot was maintainedat 0° C. to 7° C., an aqueous solution (66.2 kg, 198.0 mol) of 12.0% byweight of NaOH and a butyl acetate solution (76.5 kg, 200.0 mol) of42.3% by weight of iodine monochloride were dropped into the reactionpot over a period of 2 hours. After the end of the dropping, theresulting product was aged at 6° C. for 15 minutes. Next, the reactionproduct was filtered with use of a centrifugal filter, and a cake as aresult of the filtration was washed with 250 kg of water. The wetmaterial (composition) thus obtained containing1,3-diiodo-5,5-dimethylhydantoin had a weight of 83.3 kg. Thus obtainedwet material contained 73.3 kg (88.0% by weight) of1,3-diiodo-5,5-dimethylhydantoin, 1.3 kg (1.6% by weight) of elementaliodine, 7.3 kg (8.8% by weight) of water, and 0.8 kg (1.0% by weight) ofbutyl acetate.

Example 1

In Example 1, a halohydatoin compound was produced by drying, accordingto the following method, a halohydantoin-compound-containing compositionobtained by the method of Production Example 1.

First, 83.3 kg of a wet material of 1,3-diiodo-5,5-dimethylhydantoinobtained by the method of Production Example 1 was put in a conicalvacuum dryer having an internal capacity of 1000 L and the first stepwas carried out. The wet material contained1,3-diiodo-5,5-dimethylhydantoin whose weight was 73.3 kg (88.0 weight%), elemental iodine whose weight was 1.3 kg (1.6 weight %), water whoseweight was 7.3 kg (8.8 weight %) and butyl acetate whose weight was 0.8kg (1.0 weight %).

More specifically, first, reduction of the pressure was started andafter the degree of reduced pressure reaches a given level, a conicalvacuum dryer was rotated. At the same time, a heat medium was providedthrough a jacket of the conical vacuum dryer. Then, drying was carriedout for 6 hours. During the drying, the temperature in the dryer was ina range of 32.1° C. to 40.5° C. and the pressure in the dryer was in arange of 4.9 kPa to 6.0 kPa. Subsequently, the reduced pressure wasreturned to an ordinary pressure with nitrogen and part of a firstrefined product (crude dried product) was taken out from the conicaldryer and analyzed. As a result, it was found that the criterion basedon the organic solvent for determining the end of the first step wassatisfied because the first refined product contained 91.0 weight % of1,3-diiodo-5,5-dimethylhydantoin, 0.38 weight % of elemental iodine, and0.1 weight % of butyl acetate.

Subsequently, the second step was carried out. More specifically,reduction of the pressure was started and after the degree of reducedpressure reaches a given level, a conical vacuum dryer was rotated. Atthe same time, a heat medium was provided through the jacket of theconical vacuum dryer. Then, drying was restarted. One hour after thisrestart of drying, the temperature in the dryer reached 59.6° C.Thereafter, drying was further carried out for three hours. During this3-hour drying, the temperature in the dryer was in a range of 59.6° C.to 66.8° C. and the pressure in the dryer was in a range of 4.9 kPa to6.0 kPa. After cooling water was provided through the jacket of theconical vacuum dryer and the temperature in the dryer was cooled down to30° C., the reduced pressure was returned to an ordinary pressure withnitrogen and a second refined product (dried product) was taken out fromthe conical vacuum dryer. The weight of thus obtained second refinedproduct was 71.7 kg. The weight of 1,3-diiodo-5,5-dimethylhydantoincontained in the second refined product was 69.5 kg (97.0 weight %) andthe weight of water contained in the second refined product was 1.6 kg(2.3 weight %), but elemental iodine and butyl acetate were notdetected. The color of this second refined product was pale yellow.Further, it was found as a result of measurement by dry sieving that100% of the second refined product had a particle size of less than 8 mmand there was no particle having a particle size of not less than 8 mm.

Examples 2 Through 4

In Examples 2 through 4, by use of a wet material obtained in the samemanner as in Production Example 1, refinement was carried out in thesame manner as in Example 1. Note that Examples 2 through 4 aredifferent from Example 1 in temperature, pressure, and drying time setfor each of the first step and the second step. Table 1 showsrespectively set values and respective purities of refined productsobtained as a result of thus set values.

TABLE 1 Examples 2 3 4 Feed Amount of Fed Wet 45.5 40.0 40.0 material(kg) Purity of Wet material 88.2 88.1 88.8 (weight %) First Temperaturein Dryer (° C.) 22-41 22-39 20-42 Step Pressure in Dryer (kPa) 5.0-6.05.3-5.7 6.2-7.6 Drying Time (Hr) 6 4 5 Purity of First Refined 91.6 91.891.1 Product (weight %) Second Temperature in Dryer (° C.) 60-69 67-7166-73 Step Pressure in Dryer (kPa) 4.6-5.5 5.2-5.9 6.0-8.8 Drying Time(Hr) 6 5 6 Purity of Second Refined 95.4 97.9 96.7 Product (weight %)

As shown in Table 1, in any of Examples 2 through 4, a refined productof 1,3-diiodo-5,5-dimethylhydantoin having a high purity was obtained.Further, all the refined products were slightly colored. In addition, itwas found as a result of measurement by dry sieving that 100% of therespective second refined products had a particle size of less than 8 mmand there was no particle having a particle size of not less than 8 mm.

Example 5

In Example 5, a halohydantoin compound was produced by drying ahalohydantoin-compound-containing composition synthesized in theabove-described Production Example 1. The drying in Example 5 wascarried out by the following method.

First, 270.9 kg of a wet material of 1,3-diiodo-5,5-dimethylhydantoinobtained in the same manner as in Production Example 1 was put in aconical vacuum dryer having an internal capacity of 1000 L and the firststep was carried out.

More specifically, after the conical vacuum dryer was rotated, reductionof pressure was started. At the same time, a heat medium was providedthrough a jacket of the conical dryer. Then, drying was carried out for6 hours. During the drying, the pressure in the dryer was in a range of2.7 kPa to 4.3 kPa. Subsequently, the reduced pressure was returned toan ordinary pressure with nitrogen and part of a first refined product(crude dried product) was taken out from the conical vacuum dryer. Theweight of thus obtained first refined product was 260.2 kg. Further, thefirst refined product contained 1,3-diiodo-5,5-dimethylhydantoin whoseweight was 236.5 kg (90.9 weight %), water whose weight was 21.0 kg (8.1weight %), and butyl acetate whose weight was 0.2 kg (0.1 weight %). Ina first collection tank, 0.1 kg of elemental iodine was collected, whilein a second collection tank, 6.9 kg of water and 3.7 kg of butyl acetatewere collected.

Subsequently, the first refined product was put back into the conicalvacuum dryer and the second step was carried out. More specifically, theconical vacuum dryer was first rotated and reduction of pressure wasstarted. At the same time, a heat medium was provided through the jacketof the conical vacuum dryer. Then, drying was carried out for 6.5 hours.During the drying, the pressure in the dryer was in a range of 2.1 kPato 10.5 kPa. After cooling water was provided through the jacket of theconical vacuum dryer and the temperature in the dryer was cooled down to30° C., the reduced pressure was returned to an ordinary pressure withnitrogen and a second refined product (dried product) was taken out fromthe conical vacuum dryer. The weight of thus obtained second refinedproduct was 239.2 kg. The second refined product contained1,3-diiodo-5,5-dimethylhydantoin whose weight was 230.5 kg (96.4 weight%) and water whose weight was 2.0 kg (0.8 weight %). The color of thissecond refined product was pale yellow. Furthermore, in the firstcollection tank, 2.0 kg of elemental iodine was collected, while in thesecond collection tank, 19 kg of water was collected. The elementaliodine collected in the first collection tank was treated with alkalinesulfite aqueous solution and recovered as iodine salts and furtherrecovered as elemental iodine by chlorine oxidation of the iodine salts.

Example 6

In Example 6, a halohydantoin compound was obtained by drying ahalohydantoin-compound-containing composition obtained in the samemanner as in the Production Example 1. This drying in Example 6 wascarried out by the following method.

First, 265.29 kg of a wet material of 1,3-diiodo-5,5-dimethylhydantoinobtained in the same manner as in Production Example 1 was put in aconical vacuum dryer having an internal capacity of 1000 L and the firststep was carried out. The wet material contained1,3-diiodo-5,5-dimethylhydantoin whose weight was 236.8 kg (87.4 weight%), water whose weight was 27.9 kg (10.3 weight %), and butyl acetatewhose weight was 3.7 kg (1.4 weight %).

More specifically, the conical vacuum dryer was first rotated, andreduction of pressure was started. At the same time, a heat medium wasprovided through a jacket of the conical vacuum dryer. Then, drying wascarried out for 6 hours. During the drying, the pressure in the dryerwas in a range of 3.8 kPa to 7.1 kPa. Subsequently, the reduced pressurewas returned to an ordinary pressure with nitrogen and part of a firstrefined product (crude dried product) was taken out from the conicalvacuum dryer and analyzed. As a result, it was found that the firstrefined product contained 90.9 weight % of1,3-diiodo-5,5-dimethylhydantoin, 8.1 weight % of water, and 0.1 weight% of butyl acetate. In a first collection tank, 0.1 kg of elementaliodine was collected, while in a second collection tank, 6.9 kg of waterand 3.7 kg of butyl acetate were collected.

Subsequently, the second step was carried out. More specifically, theconical vacuum dryer was first rotated and reduction of pressure wasstarted. At the same time, a heat medium was provided through the jacketof the conical vacuum dryer. Then, drying was carried out for 6 hours.During the drying, the pressure in the dryer was in a range of 3.7 kPato 9.4 kPa. After cooling water was provided through the jacket of theconical vacuum dryer and the temperature in the dryer was cooled down to30° C., the reduced pressure was returned to an ordinary pressure withnitrogen and a second refined product (dried product) was taken out fromthe conical vacuum dryer. The weight of thus obtained second refinedproduct was 239.2 kg. The second refined product contained1,3-diiodo-5,5-dimethylhydantoin whose weight was 230.5 kg (96.1 weight%) and water whose weight was 2.0 kg (0.8 weight %). The color of thissecond refined product was pale yellow. Furthermore, in a firstcollection tank, 2.0 kg of elemental iodine was collected, while in asecond collection tank, 19 kg of water was collected. The elementaliodine collected in the first collection tank was treated with alkalinesulfite aqueous solution and recovered as iodine salts and furtherrecovered as elemental iodine by chlorine oxidation of the iodine salts.

Example 7

In Example 7, a second refined product was obtained by refining, in thesame manner as in Example 1, a halohydantoin-compound-containingcomposition obtained in the same manner as in Production Example 1. Thusobtained second refined product contained1,3-diiodo-5,5-dimethylhydantoin whose purity was 96.9 weight %, and 0.4weight % of water. Further, this second refined product was analyzed byNMR. As a result, it was found that the second refined product contained1,3-diiodo-5,5-dimethylhydantoin, 1-iodo-5,5-dimethylhydantoin,3-iodo-5,5-dimethylhydantoin and 5,5-dimethylhydantoin, and a weightratio of 1,3-diiodo-5,5-dimethylhydantoin1-iodo-5,5-dimethylhydantoin:3-iodo-5,5-dimethylhydantoin:5,5-dimethylhydantoinwas 96.9:1.1:2.0:0.0.

Comparative Example 1

In Comparative Example 1, first, 17.6 kg of1,3-diiodo-5,5-dimethylhydantoin obtained in the same manner as inProduction Example 1 was fed into a conical vacuum dryer having aninternal capacity of 200 L. This 1,3-diiodo-5,5-dimethylhydantoin had apurity of 88.7%. Then, the conical vacuum dryer was rotated andreduction of pressure was started. At the same time, heated water whosetemperature was controlled in a range of 72° C. to 74° C. was providedthrough a jacket of the conical dryer. Then, drying was carried out for9 hours. During the drying, the pressure in the dryer was in a range of7.2 kPa to 8.2 kPa. After the end of the drying, cooling water wasprovided through the jacket of the conical vacuum dryer and thetemperature in the dryer was cooled down to 30° C. Then, the reducedpressure was returned to an ordinary pressure with nitrogen. Thereafter,a dried product of 1,3-diiodo-5,5-dimethylhydantoin was taken out fromthe conical vacuum dryer. At this time, a solid colored to dark brownwas obtained in the vicinity of a manhole inlet zone or on an inner sideof a butterfly valve of the conical vacuum dryer. In addition, blackelemental iodine was also observed. It is conceivable that this blackelemental iodine was produced by decomposition of1,3-diiodo-5,5-dimethylhydantoin. As a result of analysis of the darkbrown solid, the content of 3-diiodo-5,5-dimethylhydantoin was found tobe 91.1 weight %. The dried product of 1,3-diiodo-5,5-dimethylhydantoinwas measured by dry sieving. As a result, it was found that 80% of thedried product had a particle size of less than 8 mm, 9% of the driedproduct had a particle size in a range of 8 mm to 15 mm, and 11% of thedried product had a particle size of more than 15 mm.

In Comparative example 1, the wet material was directly dried at a hightemperature under a reduced pressure as described above. It isconceivable that this resulted in decomposition of the halohydantoincompound.

Comparative Example 2

In Comparative Example 2, a halohydantoin-compound-containingcomposition obtained in the same manner as in Production Example 1 wasrefined in the same manner as in Comparative Example 1 and thereby, adried product was obtained. Thus obtained dried product ununiformlycontained a solid colored to dark brown and black elemental iodine as inComparative Example 1. In Comparative Example, a purity of1,3-diiodo-5,5-dimethylhydantoin was 91.0 weight %. Further, this driedproduct was analyzed by NMR. As a result, it was found that the driedproduct contained 1,3-diiodo-5,5-dimethylhydantoin,1-iodo-5,5-dimethylhydantoin, 3-iodo-5,5-dimethylhydantoin, and5,5-dimethylhydantoin, and a weight ratio of1,3-diiodo-5,5-dimethylhydantoin1-iodo-5,5-dimethylhydantoin:3-iodo-5,5-dimethylhydantoin:5,5-dimethylhydantoinwas 82.3:4.5:12.4:0.8. Though analysis values obtained respectively by atitration method with a 0.1 N aqueous solution of silver nitrate and NMRwere inconsistent in analysis of a low-purity product, it could beclearly confirmed from comparison with Examples that1,3-diiodo-5,5-dimethylhydantoin was decomposed during drying.

INDUSTRIAL APPLICABILITY

The present invention can be suitably applied to a method for producinga halohydantoin compound to be used as a sensitizer for a photograph orthe like, or a halohydantoin compound used as a halogenating agent or anoxidizing agent for use in a production process of medical products,agricultural chemicals, chemical products, etc.

REFERENCE SIGNS LIST

-   1 dryer-   2 a, 2 b collection tank-   3 pressure reducing pump (pressure control means)-   4 a, 4 b duct-   5 a, 5 b manometer-   6 filter (filtering means)-   7 sight glass

The invention claimed is:
 1. A recycling method including the steps ofrefining a composition containing at least one of water and elementalhalogen, an organic solvent, and a halohydantoin compound and recoveringa component removed by refining, the recycling method comprising thesteps of: (a) preparing the composition containing at least one of waterand elemental halogen, an organic solvent, and a halohydantoin compound;(b) after the step (a), removing first the organic solvent from thecomposition and then at least one of the water and the elemental halogenfrom the composition; and (c) collecting the component removed in thestep (b) and recovering the component collected, for use in the step (a)to be newly carried out, wherein the component is a combination of theorganic solvent and one of the water and elemental halogen; wherein thehalohydantoin compound is represented by the following chemical formulaI:

where: R₁ and R₂ are either identical to or different from each other,and are each independently H, a substituted or unsubstituted C1 to C10aliphatic hydrocarbon group, a substituted or unsubstituted C3 to C10alicyclic hydrocarbon group, or a substituted or unsubstituted allylgroup, or a substituted or unsubstituted C6 to C10 aralkyl group; and X₁and X₂ are either identical to or different from each other, and are (i)each independently H or a halogen atom, excluding a halohydantoincompound wherein X₁ and X₂ are both H.